This invention pertains generally to phase comparator circuitry and more particularly to phase comparator circuitry suitable for monolithic integrated circuit fabrication.
It is an object of this invention to provide an improved phase comparator circuit adapted for integrated circuit fabrication.
This and other objects of the invention are attained generally by providing, in combination: A first differential amplifier having a first input terminal adapted for coupling to an input signal source through a first input impedance, a second input terminal coupled to a predetermined voltage source, and a first output terminal; a second differential amplifier having first and second input terminals adapted for coupling to the input signal source through second and third input impedances, respectively, and a second output terminal coupled to the first output terminal; a high gain amplifier having an input coupled to the first and second output terminals and an output coupled in degenerative feedback to the first input terminal of the first differential amplifier through a first feedback impedance and also coupled in degenerative feedback to the first input terminal of the second differential amplifier through a second feedback impedance; and means responsive to a reference signal selectively to actuate the first differential amplifier to couple the input signal to the high gain amplifier through such first differential amplifier exclusively or to actuate the second differential amplifier to couple the input signal to the high gain amplifier through such second differential amplifier exclusively.